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More than a trace of oxygen; ichnological constraints on the formation of the giant Zn-Pb-Ag + or - Ba deposits, Red Dog District, Alaska

Merilie A. Reynolds, Murray K. Gingras, Sarah A. Gleeson and James U. Stemler
More than a trace of oxygen; ichnological constraints on the formation of the giant Zn-Pb-Ag + or - Ba deposits, Red Dog District, Alaska
Geology (Boulder) (August 2015) 43 (10): 867-870

Abstract

Sediment-hosted massive sulfide (SHMS) deposits are an important source of global zinc resources, and the Red Dog Pb-Zn-Ag + or - Ba district in Alaska (USA) contains giant deposits of this type. The existing model for ore formation at Red Dog involves early diagenetic replacement of sediment deposited in a restricted basin with stratified suboxic bottom waters. We present new observations of trace fossils Schaubcylindrichnus ichnospecies (isp.) and Chondrites isp. in several Red Dog deposits. The presence of the trace fossils, the size of the largest burrows, and the pervasiveness of the ichnofabric indicate that at least some intervals of the host sediment were deposited in an oxygenated middle to outer shelf environment. The burrow linings and infill are replaced by barite, hydrothermal quartz, and sulfide minerals, and the lack of compaction suggests that mineralization was diagenetically early. To reconcile these data with those from previous regional sedimentological and lithogeochemical studies, we propose a new model whereby the ore-hosting sediment was deposited in a shelfal setting in which redox conditions were affected by a fluctuating oxygen minimum zone. The strong spatial correlation between bioturbation and Red Dog SHMS deposits suggests that the presence of trace fossils may have played an important role in controlling the flow of ore-forming fluids by increasing host sediment permeability.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 43
Serial Issue: 10
Title: More than a trace of oxygen; ichnological constraints on the formation of the giant Zn-Pb-Ag + or - Ba deposits, Red Dog District, Alaska
Affiliation: University of Alberta, Department of Earth and Atmospheric Sciences, Edmonton, AB, Canada
Pages: 867-870
Published: 20150828
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 29
Accession Number: 2015-094159
Categories: Economic geology, geology of ore deposits
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2015292
Illustration Description: illus.
N67°30'00" - N67°30'00", W158°40'00" - W158°40'00"
Secondary Affiliation: Teck Resources, CAN, Canada
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201540
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